This invention relates to novel composites comprising plant material derived from members of the Parthenium spp. and plastic. Products made from composites of the instant invention may be used to make numerous items, particularly those used for construction such as lumber, plywood, poles, railroad crossties, or the like. The new composites comprising Parthenium spp. plant material and plastic are particularly useful to make wood products which exhibit resistance to termite infestation and resistance to fungal decay.
Degradation of wood, whether by insect or microbial activity, is a major problem throughout the world. Accurate economic impact of these organisms on wood damage, repair, and treatment are difficult to assess. Termite treatment in the United States costs the consumer an estimated $2 billion per year (Potter, 1997). Damage, repair, and control of the Formosan termite (Coptotermes formosanus) are estimated at $1 billion per year (Suszkiw, 1998). Other types of termites also contribute significantly to the damage of wood containing structures and components. Preventive pressurized and non-pressurized wood treatment costs approximately $5 billion per year (USDA, 1980). Wood damage by fungal rot is also in this order of magnitude (Zabel and Morrell, 1992) and the replacement is estimated to consume 10% of the timber cut annually in the United States, unnecessarily depleting the declining supply of wood. Staining and discoloration of wood by microbial activity are also of economic concern. Besides the problem of physical damage, injury to people and the decrease in real estate value must be considered.
Conventional wood preservatives and insecticides, such as copper chromate arsenate (CCA), creosote, pentachlorophenol, and cyclodiene (chlordane), used to protect wood from insect and microorganism damage, are presently of major concern to human health and the environment. Much effort has been directed to determining alternative materials to control wood damage (Carter and Huffman, 1982; Kamdem, 1994; Evans et al., 1997), but no adequate substitute has been found. Finding alternative preservatives has not been simple. A published study indicates that the natural resinous material extracted from the guayule plant (Parthenium argentatum Gray) had anti-termitic and anti-fungal properties (Bultman et al., 1991). This natural resin material is a by-product from the process for extracting rubber from the guayule shrub (Bultman et al., 1998). The application of these findings has not been commercialized. Consequently, an adequate source of this natural resin material has not been available. Similarly, other plants that have termite resistant compounds have been discovered; however, the plants are not readily cultivated for economical commercial production.
The naturally occurring resin material of the guayule plant (Parthenium argentatum) has been demonstrated to protect wood against termite, molluscan borer, and fungal attacks (Bultman et al., 1991). The latex rubber from the guayule plant has been shown to be hypoallergenic, unlike Hevea latex, and has great potential for fabricating medical products. Two USDA patents (U.S. Pat. Nos. 5,717,050 and 5,580,942; Cornish et al.) have been obtained for making medical latex products. According to Cornish (personal communication, 1998), approximately 71,000 ha of guayule shrubs must be processed per year to supply 5% of the U.S. latex glove market alone. Because only a small portion of the plant would be actually used for latex production (less than 10%), tremendous amounts of bagasse (the plant residue left after the latex is removed) will be generated. This bagasse contains quantities of the natural resin (10 to 15%) and some residual rubber (Nakayama et al., 1996). When latex processing is fully commercialized, 45 to 110 Mg hxe2x88x921 (20 to 50 tons Axe2x88x921) of waste with natural resin will be produced that must be either disposed or utilized.
The insect-controlling guayule resin is made up of a complex mixture of terpene, sesquiterpene, triterpenoid, phenolic, cinnamic, and fatty acid compounds (Schloman et al., 1983). Some of the active constituent or constituents are beginning to be identified (Gutierrez et al., 1999), but the development of the natural resin extract as a wood preservative still needs to be investigated. The impregnated natural resin extract remains in the wood for a long time (Bultman et al., 1998), an important feature of a wood preservative.
Existing wood composites prepared using traditional wood sources, recycled wood, and recovered wood have been described (see Youngquist et al., 1994; Youngquist et al., 1997, and McKeever et al., 1995).
In recent years, wood supply for making wood composites has become scarce and expensive in the United States because of competition from the paper industry for wood fiber. Thus, producers of wood composites will be forced to seek non-wood plant fibers to supply the increasing raw material requirement in the future.
Weight loss during the mycological testing of particle and fiberboards was reported as a good measure of decay resistance (Chow et al., 1980, 1993, 1994, and 1996). Walters and Chow (1975) reported that phenolic resin bonded boards are preferred in building construction for protection against water and high humidity. However, fungal attack in the phenolic bonded board was as severe as that in the urea bonded board. When composition board becomes wet, it swells mostly in thickness and in length, and considerable bonding degradation occurs.
The present invention is directed to novel composite compositions comprising plant material from Parthenium spp. and plastic. The Parthenium spp. plant material may comprise whole plants, plant parts, bagasse, or combinations thereof. The Parthenium spp. plant material may further include plant material from plants other than the genus Parthenium and/or added Parthenium spp. natural resin extract.
In making the composites of the invention, the Parthenium spp. plant material is processed, for example by mechanical or chemical reduction, dried, and then combined with the plastic in a manner so as to obtain a product wherein the Parthenium spp. plant material and plastic are bonded together and perform as a single unit.
As discussed above, it has been reported that extracted natural guayule resin has anti-termitic and anti-fungal properties, and could be used to protect wood from damage due to termites and fungi (Bultman et al., 1991). Surprisingly, however, we found that although the biological control factors reside in the natural resin extract, we obtained composites having excellent termite resistance and decay resistance by direct use of Parthenium spp. whole plant, plant parts or bagasse material to make the Parthenium spp.-plastic composites of the invention. That is, termite and fungus-resistant products were obtained while avoiding the need to extract the natural resin from Parthenium spp.
The composites of the invention comprising Parthenium spp. plant material and plastic are useful for making insect- and fungal-resistant wood products. The fabrication of this type of composite that has anti-insect, fungal, and microbial activity has not been seriously considered before. The production of insect- and rot-resistant wood is important to reduce the need to harvest wood and minimize or avoid the cost of replacing termite-damaged wood structures. Thus, the present invention fulfills a long-felt need for composites that possess insect, fungal, and other bio-resistant properties.
Products made from composites of the invention can be used to make numerous items, particularly those used for construction such as lumber, plywood, particleboard, fiberboard, poles, railroad crossties, or the like. Other products of the instant invention include storage bins for crops or other commodities; temporary housing structures; furniture components, including flat and curved surfaces; automobile and truck components; paneling for interior wall sections, partitions, and door systems; floor, wall and roof systems for light-frame construction; wall, roof, and ceiling insulation; packages, containers, cartons, and pallets; filters for air and liquids; and objects made for exterior use such as signs, sign posts, utility poles, fences, substitutes for lumber, plywood, or the like.
Accordingly, it is an object of the invention to provide composites comprising Parthenium spp. plant material and plastic.
Another object of this invention is to provide simple and effective protection from destructive organisms such as termite, fungal, or other types of infestation that can cause wood degradation by using composites comprising plant material derived from the genus Parthenium and plastic. Termite control is effected by fabricating a variety of products made from composites comprising plant material from members of the genus Parthenium and plastic.
A further object of this invention is to use the significant amounts of Parthenium spp. plant residue (bagasse) that will be generated as waste material upon commercialization of guayule for its hypoallergenic rubber latex.
A still further object of this invention is to use recyclable plastics to make the composites of the instant invention.
Still another object of this invention is to reduce the amount of raw wood material that is depleted.
Another object of the invention is to provide termite and fungus-resistant products while avoiding the need to extract the natural resin from Parthenium spp.
The following U.S. patents are incorporated by reference.
U.S. Pat. No.5,549,869 discloses a method for creating a barrier to protect wood materials by treating wood or the ground surface with a synthetic resin emulsion and an anti-fungal and wood preservative agent and/or a pesticide such as termite-controlling agent.
U.S. Pat. No. 5,612,094 discloses a method of preserving wood products by treating with a zirconium borate-containing preservative composition.